Possibly. it depends on your data:
if a user has a single occupation then the user table needs an occupation_id column
if an occupation belongs to a single user then the occupation table needs a user_id column
if a user can have many occupations and an occupation can have many users then you don't need to add columns to either of those table, but you do need to create a join table occupation_users with columns user_id and occupation_id.
You then do
has_many :occupations, :through => :occupation_users
and similarly for Occupation.